Star watchers observing the giant planet Jupiter and the
constellation Sagittarius in Michigan's evening skies this month are
actually looking into the center of our galaxy---25,000 light-years
away, according to U-M astronomer Richard Teske.

"This region of the sky contains the brightest part of the band of
the Milky Way," Teske says. "Vast numbers of faint and distant stars
are located in this area, but obscuring clouds of dusty material
floating in space between the stars prevent us from looking at the
galaxy's core directly."

The spectacle of the Milky Way in the night sky hints at our
location within the spiral galaxy that is our home, according to
Teske, who explains that our sun is an average-sized member of this
frisbee-shaped assembly of around two hundred billion stars. The sun
is located far from the galaxy's central hub, but almost exactly at
the disk's mid-plane.

"We see the bright river of the Milky Way flowing completely
around the sky, because we look out from the mid-plane," Teske says.
"Since the sun is off center, more of the distant stars congregate
toward the galaxy's middle, making the Milky Way appear brighter in
one place along its band."

The Milky Way is prominent on August evenings. This year, it is
easy to locate the galaxy's center by using the planet Jupiter as a
guide, Teske explains.

"Choose a moonless evening and a location with a clear and flat
southern horizon, away from city lights and shopping center
illumination," he says. "An hour after sunset, Jupiter is the
brightest `star' hanging low in the south. It is poised just above
the constellation of Sagittarius, the Archer, which to some looks
like a teapot. Follow the course of the Milky Way as it stretches
from overhead in the constellation Cygnus the Swan southward through
Aquila the Eagle and down into Sagittarius. From Cygnus on downward,
the Milky Way brightens and widens until our eyes come to the
galaxy's central bulge, the fattest part of the Milky Way in
Sagittarius.

"If you follow the course of the Milky Way southward from Cygnus,
you will see the `Great Rift,' a dark cleft dividing the Milky Way
into two parallel streams all the way into Sagittarius," he adds. The
dark band signifies the presence of prominent clouds of "dust" along
the Milky Way---dust whose individual motes are the size of particles
of tobacco smoke each separated from the others by distances of a
foot or two. Despite the dust's sparseness, the clouds' thickness of
hundreds of light years absorbs starlight, causing dark patches
against the Milky Way's distant stars.

"Many dust clouds congregate between our part of space and the
true center of the Milky Way galaxy," Teske explains. "Their combined
presence totally cuts off a direct view of the nucleus. What we seem
to see of the galaxy's center with our eyes, and with our
photographs, are great gatherings of stars between us and the
center---not the nucleus itself."

Even though ordinary light cannot penetrate the galaxy's dust
clouds, radio waves and infrared light navigate the dust easily.
Radio views of the galaxy's core show a fiercely energetic
environment, with circling masses of hot, magnetized gases. Images
made with infrared light depict the presence of huge numbers of stars
there, packed so densely that each is separated from its neighbors by
only a fraction of one light year.

"Images made with infrared light convey information as
understandably as ordinary pictures do, giving access to knowledge of
conditions in a region of space humans can never look upon directly,"
Teske says.